1. Field of the Invention
The present invention relates to a cable device for electrically connecting an electronic circuit board.
2. Description of the Related Art
Display devices, for example, include an electronic circuit board with an electronic circuit mounted thereon to drive a liquid-crystal display panel for displaying images. The electronic circuit includes a plurality of IC chips, for example, which are used to generate control signals for driving the liquid-crystal display panel and to generate image signals for displaying images on the liquid-crystal panel based on predetermined clock signals.
Since recent electronic circuits employ clock signals having relatively high frequencies (e.g., 10 MHz or more), the electronic circuit board including the electronic circuit is usually shielded with a shield case. In addition, a flat cable electrically connecting the electronic circuit board with other electronic circuit board is shielded by providing a ground layer. As a result, emission of extraneous clock signals having high frequencies can be prevented, which frequently occurs in use of the high frequency clock signals.
As an example for shielding a flat cable, a flexible flat cable has been used. The flat cable includes a transmission signal line pair, such as a differential signal line pair and a digital signal line pair of thin-plate conductors, which is twist-paired to form a common-mode filter to reduce an interfering component extraneously emitted from the transmission signals.
Further, Japanese Unexamined Patent Publication No. 2006-156079 discloses a flexible flat cable that forms a twisted pair by combining an analog video signal line, an audio signal line, or the like susceptible to interfering signals emitted from outside, with a ground signal line located in parallel to such an analog video signal line or an audio signal line, or the like. Further, in the flexible flat cable, a metal shield conductive layer is allowed to adhere to the outer layers of two insulating films to secure the conductor, thereby attaching both ends of the metal shield conductive layer to the ground signal line to shield the entire flexible flat cable. Thus, an interfering component extraneously emitted from a transmission signal may be reduced or an interfering component received on the transmission signal emitted from other circuits close to the flexible flat cable, devices, or the like may be suppressed.
Japanese Unexamined Patent Publication No. 2000-173828 discloses use of a flat cable core for effectively eliminating noises as well as for easily attaching a cable device to the flat cable, detaching the cable device from the flat cable, or for securing the cable device on the flat cable, and for accommodating various sizes of flat cables.